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Li Guanglei <guanglei@cn.ibm.com> writes:
> [...] > So we need deal with different Arches to get the elapsed time by > using get_cycles()
Yes, eventually recreating the complexity of gettimeofday().
> BTW, get_cycles() will return 32-bit value for some architectures > e.g ppc32, although the major architectures such as ppc64, x86, > x86_64 will all return a 64-bit value. [...]
It's even worse than that: I gather some machines return a putatively
64-bit value, but the number within overflows after a few bits past 40.
So any user of get_cycles() must correct at least for
- change in frequency
- counter overflow
- cross-CPU drift
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